The present invention relates to the field of body fluid analysis in order to monitor the concentration of analytes such as blood glucose concentration.
The invention concerns a device and system for sampling small amounts of body fluid. A body fluid sampling device comprises a skin-piercing element with a collection zone (e.g. a fluid pathway) for receiving body fluid therein. At least a portion of the collection zone is open to the environment so that fluid can be sampled. The sampling device or a separate element comprises a fluid receiving means which is out of fluidic contact with the collection zone of the skin-piercing element so that sampled fluid in the collection zone will not contact the fluid receiving means initially. The body fluid sampling device with connected collection zone or a system comprising a body fluid sampling device and fluid receiving means can be brought into a second state in which at least a portion of the collection zone contacts the fluid receiving means so that fluid is transferred. Based on signals from a test zone of the fluid receiving means analyte concentration can be determined.
Systems for sampling body fluids are already known in the prior art in which body fluid is taken up into a disposable element. Blood collection and analytical systems are known from document EP 0 199 484 for example which comprises a disposable unit with a capillary to collect body fluid and to transport the body fluid into a detection area. The further development of this concept is described in WO 97/42888. The arrangement described in this document is particularly suitable for collecting relatively small amounts of body fluids which is primarily accomplished by pressing a ring onto the area surrounding a collection site and applying a pump movement. A system for analysis based on small amounts of interstitial fluid is known from EP 0 723 418. For this purpose a very thin hollow needle is inserted into the dermis and interstitial fluid is conveyed through the needle to a test zone by applying pressure to the area surrounding the puncture site. A highly miniaturized arrangement which also utilizes a hollow needle to withdraw body fluid is known from U.S. Pat. No. 5,801,057. A particular advantage of this arrangement is the extremely thin needle which can be inserted into the arm region of a patient essentially without any pain.
Whereas the arrangement described in U.S. Pat. No. 5,801,057 already fulfils numerous practical requirements, some features are in need of improvement. A general problem with the sampling devices according to the previously mentioned document is to manufacture the hollow needle cost-effectively and as small as possible.
With this aim body fluid samplers which have an open collection zone have been contemplated. US 2003/0018282 and US 2003/0028125 both describe skin-piercing devices which have an open channel for body fluid sampling which at least partially is located in a region of a piercing needle. Body fluid sampled into the collection zone is transferred to a testing zone which is fixed to the skin-piercing element. In particular US 2003/0028125 describes that the skin-piercing element is integral with a part of a test strip. A further document that contemplates a similar sampling and testing device providing a pooling area is described in US 2002/0168290.
WO 01/72220 describes a fluid sampling and analysis device with a dermal penetration probe. Said penetration probe being in direct fluid communication with an analysis chamber. Accordingly this device design has the disadvantage that sterilization of the penetration probe which is regularly achieved by gamma radiation destroys the test chemistry located in the analysis chamber. Further sampling and analysis are spatially fixed to one another and therefore need to be close together to allow efficient sample transfer.